Problem with Andywind's picture...
Anyone who can sail will stay with him on a 5.5, maybe pass him on a 6.0 with a slalom board.
Why destroy your 7+ sail in winds of 18-28, when a smaller sail goes just as fast, jibes better, lasts longer, and is easier to sail?
At 162 lbs. and a 4/3 wetsuit, I can easily hold my 6.5 race sails when the gusts hit 30, but I'll sail for 2 hours comfortably, go just as fast, on a 5.0, jump over everyone's masts, and actually have FUN out there.

You obviously didn't get my point?! My apologies I have to express myself more clearly!
I'll try it again: with this picture I'm trying to show that RDMs matched to a good sail can be stable enough for me to:
1. Be the fastest on my pond /I am on a slalom board btw/
2. Not to have to downsize because the wind has picked up a bit
3. Have max fun and min hassle
Clearer now?
And btw did I mention that I'm now CIS free as well? Or it would be too much!?!

For most recreational sailors, intermediate - advanced in 15+ knots of wind, it doesn't make much difference in performance if you are on a RDM or SDM, as long as the sail is designed for the mast. In mismatched situations, things can get weird, but not always. Bottom line - speed and performance is more or less, 80% sailor skill.

Regardless of the mast or sail, using adjustable outhauls will extend the range of your sail, keep harness lines in balance, reduce stress and provide more time on the water. However, with 6.5 sails, the advantage is small, 7.5 - 8.5, moderate, 9.5 - 12.0, huge.

Last edited by techno900 on Fri Apr 05, 2013 9:00 am; edited 1 time in total

Two different conversations about RDM performance: Normal, high-end performance as high as PWA slalom racing almost always finds standard diameter masts the clear leader.

When I rig a 5.8 wave sail on an RDM, it feels lighter and more slippery and must be sailed differently than when rigged on a standard diameter. The std mast allows the sail to generate more power in more situations and I can keep the hammer down when going upwind and deeper downwind in chop without feeling I'm on the edge. That's not the case with the RDM. That mast requires me to feather the sail going upwind and simply runs out of steam downwind and in very wide arc jibes. All OK, but different limitations.

i did edit some of your comments. Since I prefer SDM in larger sails, 7.5+, most times 6.5 +, I tend to agree with you thought process, but I don't sail PWA , so like most everyday sailors what feels best to me , and many will never try versions of mast combos to try and extract the subtle difference in feel.

The further description, I would attribute to the mast difference in reaction to wind under a load, more so the SDM/RDM, a different SDM may very well produce similar difference in feel_________________K4 fins
4Boards....May the fours be with you

Still using std. diameter masts, SNAP OUT OF IT!!!!!!!!!! (pun intended)
RDM's are the way to go, they are so worth the money.

When I posted this, it was from my stated "biased opinion", that being from a strictly ocean/surf oriented POV, mine.

However I can see a SDM working better with a cambered race sail, assuming modern race sails still have camber inducers.
It's been awhile since I've even looked at a race sail.

I think of the leading edge of an airplane wing, and how they produce so much lift, airplane wings are blunt on the leading edge.
Then I think of how an Aeroforce sail (an indication of how long it's been for me and race sails) would work with a skinny. The lift (horizontal power) would have to be reduced due to the leading edge being too sharp.
The more distance you have between the air going over the top of a wing, or sail, and the air going under the wing, or sail, the more power, or lift, you will have.

But not being a racer, I'll happily stick with my skinnies,,,,,,,, in a very biased manner._________________I don't drink the 'cool' aid, I drink tequila, it's more honest.

Since there is a discussion on rdm vs sdm. Ever wonder how or why the size of the masts are what they are ? Were these sizes just picked radomly ? What if the masts were 10% narrower or fatter in dia ? And how much do you think (if any) does switching from sdm to rdm affect the aerodyanmics/perf of the sail? Think about a roller furling jib on a sailboat. I have read that you can roll up a jib approx 25% before it becomes advantagous to rig up a smaller jib. The reason is that the rolled up sail becomes fat, and starts to affect negatively the sail.

The mast on a windsurfing rig form the leading edge of our sails/foil. Rdm mast sharper leading edge. I wonder ???

Anyone have any thoughts ? Wonder if anyone ever took a rig into a low speed wind tunnel for testing? I remember gaastra with the rig mounted ontop of the truck years ago.

Fatter mast, more angles of attack until air drag comes into play.
Skinnies, more precise, you can feel wind changes in your hands, and have to compensate for.
What's faster?
Depends which/what sail you use. Is a wave sail inherently slower than a race sail if both are powered up?

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